we have
\[\large 0.00342 \times 10^{-5}\]
notice that we already have a '-' sign with the 10 power
now I'll take the decimal point to one step right
doing so will decrease my power by 1
\[\large 0.00342 \times 10^{-5}=00.0342\times 10^{-5-1}\]
do you get this?